Re: [PATCH 09/13] drm/i915/bdw: poll semaphores

From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Ben Widawsky <benjamin.widawsky@intel.com>
Cc: Intel GFX <intel-gfx@lists.freedesktop.org>,
	Ben Widawsky <ben@bwidawsk.net>
Subject: Re: [PATCH 09/13] drm/i915/bdw: poll semaphores
Date: Thu, 30 Jan 2014 15:26:11 +0200	[thread overview]
Message-ID: <20140130132611.GN9454@intel.com> (raw)
In-Reply-To: <1391025333-31587-10-git-send-email-benjamin.widawsky@intel.com>

On Wed, Jan 29, 2014 at 11:55:29AM -0800, Ben Widawsky wrote:
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> ---
>  drivers/gpu/drm/i915/intel_ringbuffer.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 3cfcc78..3a3ba81 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -812,6 +812,7 @@ gen8_ring_sync(struct intel_ring_buffer *waiter,
>  
>  	intel_ring_emit(waiter, MI_SEMAPHORE_WAIT |
>  				MI_SEMAPHORE_GLOBAL_GTT |
> +				MI_SEMAPHORE_POLL |
>  				MI_SEMAPHORE_SAD_GTE_SDD);

I was thinking that we shouldn't need this. However the docs suck a bit
and they don't actually specify whether the hardware will wait for the
signal before even checking the semaphore once. But that sounds so
wrong that it can't possibly be true.

>  	intel_ring_emit(waiter, seqno);
>  	intel_ring_emit(waiter,
> -- 
> 1.8.5.3
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Ville Syrjälä
Intel OTC